Binary received signals are usually evaluated with the aid of a constant threshold value. If the received signal is equal to, or exceeds a threshold value, then the received value is a logical "1". If, however, the received signal is smaller than the threshhold value, then the received value is a logical "0". If the received signal is distorted in the transmission channel due to any interfering signals or any distortion, then this method leads to erroneous and inadmissible processing results. To avoid such erroneous results, the received signal must be corrected for any distortions.
From Mese et al, U.S. Pat. No. 4,109,211, there has become known a method for slow adaption to a threshold, in which the receiver is permitted to adapt to slow changes in the received signal over a long period of time, which changes occur by a slow change of the transmission conditions in the transmission channel.